1. Field of the Invention
This invention relates to a thermal recording head used in a recording system which performs recording by utilization of heat energy.
2. Related Background Art
In the prior art, the recording system which performs recording by utilization of heat energy has the advantage of being very low in noise during recording due to the non-impact mechanism, and is also attracting attention increasingly in recent years because it enables color printing.
In such a recording system, recording information is transmitted to a thermal recording head, namely an electricity-to-heat converting device, in the form of electrical signals. As the electricity-to-heat converting device, there is employed a device comprising a heat-generating resistance layer formed on a substrate and at least one pair of electrodes connected to said heat-generating resistance layer. Here, the substrate means a material for carrying the heat-generating resistance layer, and said substrate may comprise suitable layers formed on a mere support, if desired. Since the thermal recording head is generally of relatively small size, the heat-generating resistance layer used therefor is of the thin film type, the thick film type or the semiconductor type. Particularly, the thin film type is preferable as the constituent of the thermal recording head, because power consumption is small and also thermal response is relatively good, and thus it is increasingly applied.
And, the performances demanded for such a heat-generating resistance layer of the thermal recording head are good response of heat generation to a given electrical signal, good thermal conductivity, good heat resistance to heat generation of itself and various durabilities (e.g. durability against heat history). Further, when the thermal recording head is used under pressure contact with a heat-sensitive paper or a thermal transfer ink ribbon, the coefficient of friction with those is required to be small.
Whereas, in the heat-generating resistance layer of the thermal recording head used in the prior art, the above performances are not always satisfactory and further improvement in the characteristics has been desired.
Also, in the thermal recording head of the prior art, it has been the practice to provide an abrasion-resistant layer on the surface of the heat-generating resistance layer, but such has often resulted in the sacrifice of the thermal response.
Further, in the thermal recording head of the prior art, when recording is effected on such a recording medium as a paper with coarse surface, etc., the abrasion is rapid because the head is required to strongly press in to contact with the recording medium in order to perform recording in complete dot shapes, and therefore it has been desired to improve further its performance.